摘要：

耐盐品种选育是改善次生盐渍化导致的菜心减产的措施之一,因此,对菜心耐盐品种进行筛选并明确其耐性机理。在对照及盐处理条件下,通过测定9个菜心品种的生长指标,初步比较品种间的耐盐性差异,并筛选出耐盐品种及敏盐品种。同时,比较在盐胁迫条件下耐盐品种及敏盐品种的光合特性、MDA含量、相对电导率、组织化学染色、SOD、POD、CAT、APX活性、根系活力、地上部及地下部硝酸盐含量及硝酸还原酶活性,初步阐明菜心的耐盐机理。对供试9个品种菜心的生长指标进行分析,筛选出耐盐品种连州F₁及盐敏感品种金秋红二号红;与对照(15 mmol/L Ca(NO₃)₂)处理相比,在80 mmol/L Ca(NO₃)₂胁迫下连州F₁的叶绿素含量、净光合速率、气孔导度、蒸腾速率的下降程度明显低于品种金秋红二号红;连州F₁的相对电导率、MDA含量、O₂ {\mathrm{ }}^{\frac{-}{·}}、H₂O₂的含量在Ca(NO₃)₂胁迫下增加的程度低于品种金秋红二号红,而氧自由基的清除则成相反趋势;同时,80 mmol/L Ca(NO₃)₂胁迫下连州F₁的地上及地下部分硝酸盐含量低于金秋红二号红,而硝酸还原酶的活性更高;连州F₁的根系活力受硝酸盐影响的程度低于金秋红二号红。连州F₁为耐盐型菜心品种,金秋红二号红为盐敏感型菜心品种,连州F₁所受的氧化胁迫程度较低,并且具有较高的光合效率和硝酸盐的还原能力,能够使其在硝酸盐胁迫下具有较好的生长能力,因此,在盐渍化程度较高的土地上,优先推荐连州F1作为主要栽培品种。

关键词: 菜心, 盐胁迫, 光合作用, 活性氧清除, 硝酸还原酶

Abstract:

The cultivation of salt-tolerant varieties is one of the measures to improve the yield reduction caused by secondary salinization. Therefore,the salt-tolerant varieties were screened and their tolerance mechanism were determined.Under control and salt treatment conditions,9 varieties of Brassica Campestris L. were used to compare the differences of salt-tolerance among varieties. Meanwhile,the salt-tolerant varieties and salt-sensitive varieties of Brassica Campestris L. were screened out. The photosynthetic characteristics,MDA content,relative conductivity,histochemical staining,SOD,POD,CAT,APX activity,root activity,nitrate content,and nitrate reductase activity of different varieties were determined under salt stress condition. Finally,the salt tolerance mechanism was preliminarily clarified.The growth indexes of 9 varieties were analyzed,and the salt-tolerant variety Lianzhou F₁ and salt-sensitive variety Jinqiuhong No.2 were selected. Compared with 15 mmol/L Ca(NO₃)₂ treatment (the control),the chlorophyll content,net photosynthetic rate,stomatal conductance,and transpiration rate of Lianzhou F₁ under 80 mmol/L Ca(NO₃)₂ stress were significantly lower than those of Jinqiuhong No.2. The relative conductivity,MDA content,O₂ {\mathrm{ }}^{\frac{-}{·}},and H₂O₂ content of Lianzhou F₁ had a slower degree of increasing than those of Jinqiuhong No.2 under Ca(NO₃)₂ stress,while the scavenging of oxygen free radicals had an opposite trend. Compared with the control,the increase of nitrate content in the shoot and root of Lianzhou F₁ under 80 mmol/L Ca(NO₃)₂ stress was lower than that of Jinqiuhong No.2,while the activity of nitrate reductase showed an opposite trend. Moreover,the root activity of Lianzhou F₁ was less affected by nitrate than Jinqiuhong No.2.Lianzhou F₁ is a salt-tolerant Brassica Campestris L. variety,and Jinqiuhong No.2 is a salt-sensitive variety. Lianzhou F₁ has a low degree of oxidative stress,and a high photosynthetic efficiency and nitrate reducing ability,which can make it have a good growth ability under nitrate stress. Therefore,in the land with high degree of salinization,Lianzhou F₁ was recommended as the main cultivar.

Key words: Brassica Campestris L., Salt stress, Photosynthesis, Reactive oxygen scavenging, Nitrate reductase